FIG 6.

Cross-reactive envelope-specific antibodies do not elicit Fc-mediated responses. Sera from TBEV vaccinated patients were analyzed for binding to ZIKV proteins and the ability to elicit Fc-mediated effector functions. Sera were obtained through a screening of TBEV vaccinee samples as described previously in the work of Duehr et al. (49). ELISAs were performed on recombinant ZIKV envelope protein (A) or recombinant NS1 protein from PRVABC59 ZIKV (B). All sera were tested at a starting dilution of 1:40 and were serially diluted 4-fold in duplicate. “Acute ZIKV Infection” indicates serum from a patient with an acute infection confirmed by reverse transcription-PCR. (C) Vero cells were infected with PRVABC59 ZIKV, and a surrogate in vitro reporter assay was performed to measure Fc-FcγR interactions. All sera were tested at a starting dilution of 1:25 and were serially diluted 3-fold in duplicate.